What is Shape Memory?

Tubing manufactured from shape memory alloy

Shape memory is a property of select materials that have the ability to "remember" the shape given during original thermo-mechanical processing allowing the material to revert to that original shape when subjected to heat.

Materials with shape memory properties allow for the creation of lightweight solid-state devices that would otherwise require the use of mechanical systems.

Shape Memory Alloy

Johnson Matthey Medical Components specializes in NiTi, or nickel-titanium shape memory alloys, commonly referred to as nitinol. Other common SMA's include copper-zinc-aluminum-nickel and copper-aluminum nickel. Shape memory alloy is commonly known as, and marketed under, the following names:

  • SMA
  • smart metal
  • memory metal
  • memory alloy
  • muscle wire
  • smart alloy

Wire manufactured from shape memory alloy

Nickel titanium, or Nitinol, properties include the shape memory effect, superelasticity, and high damping capability. By changing composition, mechanical working, and applying heat treatment these technical properties of NiTi shape memory alloys can be modified to a great extent to suit the specific application of Johnson Matthey's clients.

Shape Memory Alloy Applications

Many of Johnson Matthey Medical Components' customers incorporate these special shape memory and super-elastic properties into a variety of medical applications from orthodontics to endovascular surgery. Possible applications of shape memory and super-elastic alloys include:

  • Catheter shafts
  • Stents
  • Valve frames
  • Needles
  • Orthodontic guidewires
  • Endoscopic guide tubes
  • Occluders
  • Retrievers
  • Distal protection
  • Laproscopes

If you would like more information regarding the properties or supply of SMA's, please click the 'contact us' icon in the left column.

Manufacture of Shape Memory Alloys

Johnson Matthey Medical Components' shape memory alloys are formed by blending the alloy and then induction melting in an inert-atmosphere vacuum chamber. Further processing is done to form wire, ribbon, sheet or laser machined components.

Once processed to its finished form, shape memory alloys are "trained" to exhibit the specific properties required by the client's SMA application. The shape memory training process determines the shape that the alloy will recall and revert to when subjected to a specific heat point.

In Johnson Matthey Medical Components' Nickel Titanium shape memory alloys, the temperature at which the SMA remembers its high-temp form can be adjusted by heat treatment and variations in the alloy composition from 0°C to +105°C maximum. The shape recovery happens over a range of just a few degrees, with shape recovery start/end points controllable within a few degrees centigrade.

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